Chen Xiu-Lan, Dong Sheng, Xu Fei, Dong Fang, Li Ping-Yi, Zhang Xi-Ying, Zhou Bai-Cheng, Zhang Yu-Zhong, Xie Bin-Bin
State Key Laboratory of Microbial Technology, Shandong UniversityJinan, China; Marine Biotechnology Research Center, Shandong UniversityJinan, China.
State Key Laboratory of Microbial Technology, Shandong UniversityJinan, China; Marine Biotechnology Research Center, Shandong UniversityJinan, China; Institute of Marine Science and Technology, Shandong UniversityJinan, China.
Front Microbiol. 2016 Jul 19;7:1120. doi: 10.3389/fmicb.2016.01120. eCollection 2016.
Marine bacterial alginate lyases play a role in marine alginate degradation and carbon cycling. Although a large number of alginate lyases have been characterized, reports on alginate lyases with special characteristics are still rather less. Here, a gene alyPM encoding an alginate lyase of polysaccharide lyase family 7 (PL7) was cloned from marine Pseudoalteromonas sp. SM0524 and expressed in Escherichia coli. AlyPM shows 41% sequence identity to characterized alginate lyases, indicating that AlyPM is a new PL7 enzyme. The optimal pH for AlyPM activity was 8.5. AlyPM showed the highest activity at 30°C and remained 19% of the highest activity at 5°C. AlyPM was unstable at temperatures above 30°C and had a low T m of 37°C. These data indicate that AlyPM is a cold-adapted enzyme. Moreover, AlyPM is a salt-activated enzyme. AlyPM activity in 0.5-1.2 M NaCl was sixfolds higher than that in 0 M NaCl, probably caused by a significant increase in substrate affinity, because the K m of AlyPM in 0.5 M NaCl decreased more than 20-folds than that in 0 M NaCl. AlyPM preferably degraded polymannuronate and mainly released dimers and trimers. These data indicate that AlyPM is a new PL7 endo-alginate lyase with special characteristics.
海洋细菌藻酸盐裂解酶在海洋藻酸盐降解和碳循环中发挥作用。尽管已经鉴定出大量的藻酸盐裂解酶，但关于具有特殊特性的藻酸盐裂解酶的报道仍然较少。在此，从海洋假交替单胞菌属菌株SM0524中克隆了一个编码多糖裂解酶家族7（PL7）藻酸盐裂解酶的基因alyPM，并在大肠杆菌中进行表达。AlyPM与已鉴定的藻酸盐裂解酶的序列同一性为41%，表明AlyPM是一种新的PL7酶。AlyPM活性的最适pH为8.5。AlyPM在30°C时表现出最高活性，在5°C时仍保持最高活性的19%。AlyPM在温度高于30°C时不稳定，其熔解温度（T m）较低，为37°C。这些数据表明AlyPM是一种冷适应酶。此外，AlyPM是一种盐激活酶。在0.5 - 1.2 M NaCl中AlyPM的活性比在0 M NaCl中高6倍，这可能是由于底物亲和力显著增加所致，因为AlyPM在0.5 M NaCl中的米氏常数（K m）比在0 M NaCl中降低了20多倍。AlyPM优先降解聚甘露糖醛酸，主要释放二聚体和三聚体。这些数据表明AlyPM是一种具有特殊特性的新的PL7内切藻酸盐裂解酶。
